A translation memory (TM) is a database that stores previously completed translations so they can be reused in future projects.
Its purpose is to increase consistency, quality, and efficiency in the translation process by eliminating the need to retranslate sentences or text fragments that have already been translated before.
Within a translation memory, the information is organized into translation units (TUs).
Translation Units (TUs)
A segment is a piece of text in one language, usually a sentence, phrase, or short string of text. When you take a segment in the source language and its corresponding translation in the target language, together they form a translation unit.
1. Translation Unit (TU) = the source segment + its translated target segment.
2. Segment = a piece of text in a single language.